Moulding process

Abstract

A highly effective and cost-effective method and apparatus for manufacturing soft contact lenses by physically forming the lenses form sheet (or other solid) material in a batch or continuous process.

1. A method of producing a plurality of soft contact lenses comprising the steps of:
 A. providing a sheet of solid, substantially dry material; 
 B. forming said material into a plurality of shaped lens blanks through controlled application of physical force to the material by compression of the material between a plurality of form or platen pairs arranged in an array to simultaneously press together the material into a plurality of shaped lens blanks in a process selected from the group consisting of thermoforming, vacuum forming, pressing, hot moulding, cold moulding, and compression moulding; and 
 C. hydrating said plurality of shaped lens blanks; 
 wherein at least immediately subsequently to said physical forming step B, said plurality of shaped lens blanks remain at least partially attached to the sheet of material and the sheet is used as a transport medium or carrying mechanism for said plurality of shaped lens blanks. 
 
     
     
       2. A method of producing a plurality of soft contact lenses according to  claim 1 , wherein said sheet of solid substantially dry material is water soluble above a certain temperature, and formed into said plurality of shaped lens blanks at a temperature below said certain temperature. 
     
     
       3. A method of producing a plurality of soft contact lenses according to  claim 2 , in which said certain temperature is approximately 50° C. 
     
     
       4. A method of producing a plurality of soft contact lenses according to  claim 2 , in which said certain temperature is approximately 65° C. 
     
     
       5. A method of producing a plurality of soft contact lenses according to  claim 1 , in which the said material is chosen from the group consisting of polyvinyl alcohol or a copolymer of polyvinyl alcohol and polyvinyl acetate or polyethylene-maleic-anhydride or polymethyl-hydroxy-propyl-cellulose or copolymers of methyl acrylate or ethyl acrylate with ethylene or their hydroxyl derivatives. 
     
     
       6. A method of producing a plurality of soft contact lenses according to  claim 1 , in which said material is a copolymer of polyvinyl alcohol and polyvinyl acetate where the degree of hydrolysis, as measured by saponification, is at least 96% mol based on the original polyvinyl alcohol. 
     
     
       7. A method of producing a plurality of soft contact lenses according to  claim 1 , in which said material is a substantially uncrosslinked polymer comprising crosslinkable groups and in which, prior to the hydration step C, high energy is applied to said plurality of shaped lens blanks, whereby said polymer is crosslinked to a predetermined, desired crosslink density. 
     
     
       8. A method of producing a plurality of soft contact lenses according to  claim 7 , in which the material contains additives that react to the application of high energy to improve crosslinking efficiency. 
     
     
       9. A method of producing a plurality of soft contact lenses according to  claim 7 , in which the application of high energy involves irradiation of the plurality of shaped lens blanks by a form of high energy chosen from the group consisting of electron beam irradiation or gamma irradiation or microwave irradiation or ultraviolet irradiation or infrared irradiation or thermal irradiation or ultrasound irradiation. 
     
     
       10. A method of producing a plurality of soft contact lenses according to  claim 1 , wherein said plurality of shaped lens blanks are fully removed from the sheet at a stage after step B by the use of a laser cutting device. 
     
     
       11. A method of producing a plurality of soft contact lenses according to  claim 1 , in which said physical forming step B comprises the following substeps:
 B.1 heating said material to a temperature that: 
 a) is near to the softening temperature of the material, whereby thermoforming of said material is possible, but b) is below the melting point of said material, whereby the physical integrity of said material is maintained; and 
 B.2 thermoforming said plurality of shaped lens blanks through application of physical force to said material. 
 
     
     
       12. A method of producing a plurality of soft contact lenses according to  claim 11 , in which said thermoforming sub-step involves compression of the material between two forms or platens. 
     
     
       13. A method of producing a plurality of soft contact lenses according to  claim 1 , in which the physical forming step B involves the use of moulds and said material is placed between said moulds which are pressed together to form said plurality of shaped lens blanks. 
     
     
       14. A method of producing a plurality of soft contact lenses according to  claim 1 , in which high energy is applied to said plurality of shaped lens blanks and/or to said plurality of soft contact lenses in order to sterilise them. 
     
     
       15. A method of producing a plurality of soft contact lenses according to  claim 14 , in which the application of high energy involves irradiation by a form of high energy chosen from the group consisting of electron beam irradiation or gamma irradiation or microwave irradiation or ultraviolet irradiation. 
     
     
       16. A method of producing a plurality of soft contact lenses according to  claim 1 , which comprises the further step of:
 D. transferring the plurality of shaped lens blanks to a plurality of final packs. 
 
     
     
       17. A method of producing a plurality of soft contact lenses according to  claim 16 , in which, before the transferring step D, the final packs are sterilised. 
     
     
       18. A method of producing a plurality of soft contact lenses according to  claim 17 , in which, either before or after the transferring step D, aseptic or sterile solution is added to the sterile final packs which solution acts to hydrate the lenses in step C. 
     
     
       19. A method of producing a plurality of soft contact lenses according to  claim 16 , in which the material of the shaped lens blanks undergoes a chemical reaction in the final packs. 
     
     
       20. A method of producing a plurality of soft contact lenses according to  claim 1 , in which all process steps subsequent to step B are carried out without further human contact or handling. 
     
     
       21. A method of producing a plurality of soft contact lenses according to  claim 1 , which method is automated or semi-automated to run in a continuous or semi-continuous manner. 
     
     
       22. A method of producing a plurality of soft contact lenses according to  claim 1 , which further involves quality control inspections on the shaped lens blanks only. 
     
     
       23. A method of producing a plurality of soft contact lenses according to  claim 22 , which involves either visual quality control inspections or quality control inspections using an optical system. 
     
     
       24. A method of producing a plurality of soft contact lenses according to  claim 19 , in which the material undergoes a hydrolysis reaction in the final packs.